Invention: Slimline radioactive battery

Engineers have long hoped to exploit radioactive decay to generate electricity. One way to do this is to use a radioactive isotope, such as a variant of hydrogen called tritium, that emits electrons as it decays. Current is generated when the electrons hit semiconductive material nearby.

Attempts to put the theory into practice have been plagued by extremely low efficiency, though, converting only a small fraction of the emitted electrons into current.

The problem is that the electrons cannot travel far from their starting place in the tritium nucleus. Most end up lodging in the radioactive material itself and never reach the adjacent semiconductor.

Now Paul Engel and colleagues at Rice University in Houston, Texas, say that these batteries can be made more efficient by using a thin layer of a liquid polymer that contains the isotope.

Electron catcher

The polymer can be painted onto the surface of a porous semiconductor, creating a very thin layer of radioactive material that soaks into the pores. This minimises the distance between decaying nuclei and the semiconductor, so electrons are much more likely to be caught and turned into current.

The use of thin layers means that the batteries can be made into a wide range of shapes, such as thin sheets.

The beta radiation produced by tritium and similar materials is easily contained too. Even if the casing of a battery was breached, the close bond between the polymer and the semiconductor would keep the radioactive material firmly in place.

The patent claims that the resulting batteries could have a range of uses, either as the sole power source or a "trickle-charger" to make a normal chemical battery last longer. Long-lived gadgets in inaccessible places like spacecraft, deep-sea sensors, or even medical implants, would be ideal places, it says.

If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.